This invention relates to a method and composition for treating fobrics to impart improved heat transfer printability thereto and to the heat transfer printing of fabrics which have been so-treated.
Heat transfer printing is a method commonly used in the textile industry to impart a desired color pattern to a fabric substrate. In accordance with this method, a color pattern to be imparted to the fabric substrate, e.g., a woven or knitted material or carpet, is initially prepared as a print on a heat transfer sheet, conventionally paper. The inks used for preparing the printed pattern are selected to volatilize or sublime at a temperature acceptable to the fabric substrate. The transfer sheet is placed in contact with the fabric to be printed and heat is applied. As a result, the inks are transferred by heat to the fabric. The fabric must be of such a nature that it will receive and retain the transferred inks, so as to give a permanent print on the fabric. The mechanism of the transfer step is believed to be that the gases resulting from volatization or sublimation of the respective inks are absorbed by at least the outer surface layers of the individual fibers of the fabric. This effect can readily be obtained on many fabrics made from synthetic fibers, especially polyester fibers. As a result, large quantities of polyester fabric printed in this manner have been produced commercially. The method is relatively quick, simple to carry out, cheap in materials and labor, and results in a good permanent print in as many colors as are imparted to the original transfer sheet, and further results in low effluent wastes.
On the other hand, this technique has met with considerable difficulty when applied to fabrics containing cellulosic fibers such as cotton, rayon and cellulose acetate; wool and other animal fibers; and other natural fibers such as silk and blends of such cellulosic and/or natural fibers with polyester and other synthetics. Primarily such blends are of a polyester and cotton, but others are within the scope of this disclosure. When transfer printing is attempted on fabrics containing such cellulosic and/or natural fibers and blends, the resulting print has been generally poor because the disperse dyes do not adhere to the natural and/or cellulosic fibers.
As a result of the foregoing, numerous attempts have been made in the past to improve the heat transfer printing characteristics of textile fabrics containing the aforementioned cellulosic and natural proteinaceous fibers. Such prior art attempts have generally included resin pre-treatment such as that disclosed in U.S. Patent 4,492,584 to Jenkins (issued January 8, 1985; various crosslinking treatments such as those discussed within the Background of the Invention section of the indicated Jenkins's patent; and chemical modification treatment (e.g., cyanoethylation or benzoylation) as discussed in the article by Prof. Dr. H. Herlinger entitled "Transfer Printing-Present Stage of Technical Development and Future Development Trends", Melliand Textilberichte [English Edition], November, 1980, pages 1487-1494.
Prior art attempts have also included the use of polyhydric alcohols and derivatives thereof such as polyethylene glycol and polyethylene glycol monoethers as swelling agents for cellulosic fiber-containing fabric materials. However, according to the aforementioned article by Dr. Herlinger, the wash fastness of transfer printed cellulosic fabric subjected solely to swelling agent pre-treatment is very poor. Additionally, the present inventors have observed that transfer printed cellulosic fabric subjected solely to such conventional polyhydric alcohol swelling pre-treatment is also generally deficient in its colorfastness to dry and wet crocking.